The standard yardstick for judging housing affordability is to look at the median level of rents or home prices. As we all remember from statistics, the median is the observation in the middle of the distribution. And while for many purposes, it’s a reliable indicator of typical prices, in some neighborhoods, particularly those with a mix of expensive and cheap housing, the median is actually a weak indicator of affordability. — City Observatory
"For an illustration of this problem, imagine two neighborhoods. In both places, the median home costs $300,000. But in the first neighborhood, every home costs exactly $300,000, while in the second, there are a range of homes from $100,000 to $500,000. Although both neighborhoods have the same median home price, the second neighborhood has some homes affordable to low-income people, while the first neighborhood does not. So rather than the median, or 50th percentile, home price, we really care about something like the 25th percentile: the home for which 75 percent of homes are more expensive."